Solid electrolyte and method for producing the same

Abstract

The present invention relates to a solid electrolyte and a manufacturing method thereof. More specifically, the solid electrolyte includes a mixed conductive polymer having ionic conductivity and electrical conductivity properties and a binder, and thereby adhesion and strength are enhanced, and thus interfacial resistance can be reduced and ionic conductivity can be improved.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2021-0174998 filed on December 8, 2021, and Korean Patent Application No. 2022-0169893 filed on December 7, 2022, and all the contents disclosed in the corresponding Korean patent application documents are incorporated herein by reference in their entirety.

[0002] The present invention relates to a solid electrolyte and a method for manufacturing the same.

Background Art

[0003] From the viewpoints of battery capacity, safety, output, large-scale, and ultra-small scale, various batteries that can overcome the limitations of lithium secondary batteries are currently being studied.

[0004] Typically, compared with current lithium secondary batteries, metal-air batteries with a very large theoretical capacity in terms of capacity, all solid batteries without the risk of explosion in terms of safety, supercapacitors in terms of output, NaS batteries or RFB (redox flow batteries) in terms of large-scale, and thin film batteries in terms of ultra-small scale are being continuously studied.

[0005] Among these, an all solid battery means a battery in which the liquid electrolyte used in existing lithium secondary batteries is replaced with a solid electrolyte. Since a flammable solvent is not used in the battery, ignition and explosion due to decomposition reactions of conventional electrolytes do not occur at all, so safety can be greatly improved. In addition, since Li metal or Li alloy can be used as the negative electrode material, there is an advantage that the energy density with respect to the mass and volume of the battery can be epochally improved.

[0006] Thus, all-solid-state batteries have the advantage of improved safety compared to conventional batteries using liquid electrolytes. However, it is not easy to ensure the ionic conductivity of the solid electrolyte contained in the all-solid-state battery, and there are limitations in significantly improving the energy density and lifespan of all-solid-state batteries using commercially available solid electrolytes.

[0007] In particular, in order to be applied for the use of an electrolyte membrane rather than an electrode in an all-solid-state battery, it is necessary to improve the ionic conductivity of the solid electrolyte. Generally, however, there is a problem that the electrical conductivity increases due to the interfacial resistance of the solid electrolyte, and the ionic conductivity somewhat decreases.

[0008] Therefore, there is a need for the development of a technology that can reduce the interfacial resistance of the solid electrolyte and improve the ionic conductivity.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] As a result of conducting extensive research to solve the above problems, the inventors of the present invention have confirmed that by using a mixed-conductive polymer, a binder, and a lithium salt having ionic conductivity and electrical conductivity characteristics and controlling them within an appropriate content range, it is possible to manufacture a solid electrolyte with reduced interfacial resistance and improved ionic conductivity.

[0011] Therefore, an object of the present invention is to provide a solid electrolyte with improved ionic conductivity and a method for manufacturing the same.

[0012] Another object of the present invention is to provide an all-solid-state battery including the solid electrolyte.

Means for Solving the Problems

[0013] To achieve the above object, the present invention provides a solid electrolyte containing a mixed conductive polymer having characteristics of ionic conductivity and electric conductivity, a binder, and a lithium salt.

[0014] The mixed conductive polymer may include one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), polyacetylene, poly(paraphenylene), poly(paraphenylene)sulfide, polythiophene, polypyrrole, polyisothianaphtalene, poly(paraphenylene vinylene), polyaniline, and poly(3,4-ethylenedioxythiophene).

[0015] The binder may contain one or more selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphagen, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride and poly(vinylidene fluoride)-hexafluoropropene.

[0016] The lithium salt is LiTFSI (Lithium bis(trifluoromethanesulphonyl)imide), LiFSI (Lithium bis(fluorosulfonyl)imide), LiNO 3 , LiOH, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO3 Li, CF 3 SO 3 Li, LiSCN, LiC(CF 3 SO 2 ) 3 、(CF 3 SO 2 ) 2 NLi and (FSO 2 ) 2 It may contain one or more selected from the group consisting of NLli.

[0017] The solid electrolyte may contain 100 parts by weight of the mixed conductive polymer, 2 to 30 parts by weight of a binder, and 5 to 300 parts by weight of a lithium salt with respect to 100 parts by weight of the mixed conductive polymer.

[0018] The solid electrolyte may contain 100 parts by weight of the mixed conductive polymer, 2 to 30 parts by weight of a binder, and 100 to 300 parts by weight of a lithium salt with respect to 100 parts by weight of the mixed conductive polymer.

[0019] The solid electrolyte may be in a form in which a lithium salt is dissociated and contained inside a mixed conductive polymer matrix containing a mixed conductive polymer and a binder.

[0020] The solid electrolyte may be in the form of a solid electrolyte membrane.

[0021] The thickness of the solid electrolyte may be 10 to 60 μm.

[0022] The present invention also provides a method for manufacturing a solid electrolyte, including: (S1) coating a mixed solution obtained by adding a mixed conductive polymer, a binder, and a lithium salt to a solvent onto a substrate; and (S2) drying the coating layer obtained in the step (S1).

[0023] The coating method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, or solution casting.

[0024] The drying may be performed at 300°C or lower.

[0025] The substrate may be stainless steel, polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

[0026] The solvent may be one or more selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, N,N-dimethylformamide (DMF), benzene, tetrahydrofuran (THF), and water.

[0027] The present invention also provides an electrode for an all-solid-state battery having a coating layer containing the solid electrolyte formed thereon.

[0028] The electrode may be a positive electrode or a negative electrode.

[0029] The present invention also provides an all-solid-state battery including the electrode.

Advantages of the Invention

[0030] The solid electrolyte according to the present invention shows the effect that the adhesive force and strength are improved by a binder, the interfacial resistance is reduced, and thereby the ionic conductivity is improved.

[0031] In addition, by controlling the content ratio of the mixed-conducting polymer and the lithium salt, the ionic conductivity and the electric conductivity of the solid electrolyte can be adjusted.

Brief Description of the Drawings

[0032]

Figure 1

Embodiments for Carrying Out the Invention

[0033] Hereinafter, the present invention will be described in more detail to facilitate understanding of the present invention.

[0034] Terms and words used in this specification and the claims should not be construed as being limited to ordinary or dictionary meanings, and should be construed in a meaning and concept consistent with the technical idea of the present invention in accordance with the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way.

[0035] Solid electrolyte The present invention relates to a solid electrolyte.

[0036] The solid electrolyte according to the present invention includes a mixed-conducting polymer, a binder, and a lithium salt. The solid electrolyte may be a polymer solid electrolyte.

[0037] The solid electrolyte according to the present invention can have its ionic conductivity improved by enhancing the adhesive force and strength by the binder, thereby reducing the interfacial resistance.

[0038] The solid electrolyte has a form in which a lithium salt is dissociated in a mixed-conductive polymer matrix containing a mixed-conductive polymer and a binder, and the cations and anions of the lithium salt exist in a dissociated state.

[0039] In the present invention, the mixed-conductive polymer has a mixed-conductive property including ionic conducting and electronic conducting properties, and can simultaneously serve as a conductive material for moving electrons and an electrolyte for moving lithium ions.

[0040] The mixed-conductive polymer may include one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), polyacetylene, poly(paraphenylene), poly(paraphenylene)sulfide, polythiophene, polypyrrole, polyisothianaphtalene, poly(paraphenylene vinylene), polyaniline, and poly(3,4-ethylenedioxythiophene).

[0041] For example, the mixed conductive polymer may be poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)), and in the PEDOT:PSS, the weight ratio of PEDOT to PSS may be 1:1 to 4, 1:1.5 to 3.5, 1:2 to 3, or 1:2.5.

[0042] In the present invention, the binder reduces the crystallinity of the conductive polymer and increases the fluidity (mobility). Further, the binder can improve the ionic conductivity by improving the adhesion and strength of the solid electrolyte and reducing the interfacial resistance.

[0043] The binder can include one or more selected from the group consisting of styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphagen, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder can include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate and polyvinylidene fluoride.

[0044] Also, the binder can be contained in an amount of 2 to 30 parts by weight with respect to 100 parts by weight of the mixed conductive polymer. Specifically, the content of the binder may be 2 parts by weight or more, 3 parts by weight or more, 5 parts by weight or more, or 10 parts by weight or more, and may be 15 parts by weight or less, 20 parts by weight or less, 25 parts by weight or less, or 30 parts by weight or less. If the content of the binder is less than 2 parts by weight, the degree of improvement in the adhesive force and strength of the solid electrolyte is negligible, and the effect of reducing the interfacial resistance may not be good. If it exceeds 30 parts by weight, the effect of the binder with low electrical conductivity becomes large, and conversely, the electrical conductivity may be significantly reduced.

[0045] In the present invention, the lithium salt can serve as a lithium source that dissociates in the mixed conductive polymer matrix to allow lithium ions to exist.

[0046] The lithium salt is LiTFSI (Lithium bis(trifluoromethanesulphonyl)imide), LiFSI (Lithium bis(fluorosulfonyl)imide), LiNO 3 , LiOH, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, LiSCN, LiC(CF 3 SO 2 ) 3 , (CF 3 SO 2 ) 2 NLi and (FSO 2 ) 2It may also contain one or more selected from the group consisting of NLi.

[0047] Further, the lithium salt can be contained in an amount of 5 to 300 parts by weight with respect to 100 parts by weight of the mixed conductive polymer. Specifically, the content of the lithium salt may be 5 parts by weight or more, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 70 parts by weight or more, or 100 parts by weight or more, and may be 120 parts by weight or less, 130 parts by weight or less, 140 parts by weight or less, 150 parts by weight or less, 200 parts by weight or less, 250 parts by weight or less, or 300 parts by weight or less. If the content of the lithium salt is less than 5 parts by weight, the lithium source may be insufficient and the ionic conductivity may be significantly reduced. If it exceeds 300 parts by weight, the excess lithium salt that has not dissociated in the mixed conductive polymer may precipitate and the ionic conductivity may decrease.

[0048] In the present invention, the solid electrolyte is in the form of a solid electrolyte membrane and can be used as an electrolyte of an all-solid-state battery or applied to an electrode. When the solid electrolyte is applied to an electrode, it can be formed on the active material layer of the positive electrode or the negative electrode, or formed inside.

[0049] In the present invention, the thickness of the solid electrolyte may be 10 to 60 μm. Specifically, the thickness of the solid electrolyte may be 10 μm or more, 15 μm or more, or 20 μm or more, and may be 40 μm or less, 50 μm or less, or 60 μm or less. If the thickness of the solid electrolyte is less than 10 μm, the strength may become weak, and if it exceeds 60 μm, the energy density may decrease.

[0050] Method for manufacturing a solid electrolyte The present invention also relates to a method for manufacturing a solid electrolyte. The method for manufacturing the solid electrolyte includes: (S1) coating a mixed solution obtained by adding a mixed conductive polymer, a binder, and a lithium salt to a solvent onto a substrate; and (S2) drying the coating layer obtained in the step (S1).

[0051] Hereinafter, the method for manufacturing a solid electrolyte according to the present invention will be described in more detail for each stage.

[0052] In the present invention, in the step (S1), a mixed solution obtained by adding a mixed conductive polymer, a binder, and a lithium salt to a solvent can be coated on a substrate. The types and contents of the mixed conductive polymer, the binder, and the lithium salt are as described above.

[0053] FIG. 1 is a schematic diagram showing a process of forming a coating layer for manufacturing a solid electrolyte film on a substrate according to an embodiment of the present invention.

[0054] Referring to FIG. 1, after dissolving a mixed conductive polymer in a solvent to produce a mixed conductive polymer solution (polymer solution), a lithium salt (Li salt) can be mixed to obtain a first mixed solution (Polymer / Li salt solution).

[0055] The mixing can be carried out until the first mixed solution appears uniform to the naked eye. For example, the mixing can be carried out for 8 to 16 hours. Specifically, the mixing time may be 8 hours or more, 9 hours or more, or 10 hours or more, and may also be 14 hours or less, 15 hours or less, or 16 hours or less. If the mixing time is less than 8 hours, the first mixed solution cannot become a uniform state, and if it exceeds 16 hours, even if the mixing time increases, there is no significant change in the uniformity of the first mixed solution, so the efficiency may be reduced in terms of processability.

[0056] Thereafter, a binder (binder) can be mixed with the first mixed solution (Polymer / Li salt solution) to obtain a second mixed solution (Polymer / Li salt / binder solution), and then it can be coated on a substrate.

[0057] The solvent is not particularly limited as long as it can dissolve and / or disperse the mixed conductive polymer, binder, and lithium salt to form a solution. For example, the solvent may be one or more selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, N,N-dimethylformamide (DMF), benzene, tetrahydrofuran (THF), and water. The usage amount of the solvent can be adjusted in consideration of the coating thickness of the coating layer, the physical properties of the solid electrolyte to be produced, and the like.

[0058] Also, the concentrations of the first mixed solution and the second mixed solution are not particularly limited as long as the coating process can be carried out. For example, the concentrations of the first mixed solution and the second mixed solution may be from 0.5% to 30%, specifically, may be 0.5% or more, 1% or more, or 3% or more, or may be 10% or less, 20% or less, or 30% or less. If the concentration of the mixed solution of the first mixed solution and the second mixed solution is less than 0.5%, the formed coating layer may be too thin, and if it exceeds 30%, it may be difficult to form the coating layer uniformly. The concentrations of the first mixed solution and the second mixed solution may be the same or different.

[0059] The coating method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, or solution casting, but is not limited thereto as long as it is a coating method capable of forming a coating layer on the substrate.

[0060] Also, the substrate is not particularly limited as long as it can be used to form the coating layer. For example, the substrate may be stainless steel, polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

[0061] In the present invention, in the step (S2), the coating layer obtained in the step (S1) can be dried.

[0062] The drying is not particularly limited as long as it is a drying method capable of evaporating the solvent contained in the coating layer to form a coating layer for solid electrolyte formation. For example, the drying may be carried out at 300°C or lower. Specifically, the drying temperature may be 300°C or lower, 200°C or lower, 150°C or lower, or 100°C or lower. The drying temperature may vary depending on the type of solvent and the drying conditions. For example, in the case of vacuum drying, it can be carried out at 100°C or lower. Also, when the solvent is acetones or alcohols, it can also be carried out at 100°C or lower. If the drying temperature exceeds 300°C, the solid electrolyte may be thermally decomposed. The lower limit of the drying temperature is not particularly limited, but for example, it may be 60°C or higher.

[0063] In the present invention, after the step (S2), the step (S3) can be further carried out. In the step (S3), after the drying in the step (S2), the coating layer can be separated from the substrate to obtain a solid electrolyte.

[0064] Electrode for all-solid-state battery and all-solid-state battery including the same The present invention also relates to an electrode for an all-solid-state battery having a coating layer containing the solid electrolyte. The electrode is a positive electrode or a negative electrode.

[0065] In the present invention, the positive electrode may include a positive electrode active material layer and a coating layer including the solid electrolyte formed on one surface of the positive electrode active material layer. The coating layer may be formed by attaching the solid electrolyte manufactured by the manufacturing method as described above to the positive electrode active material layer, or may be formed by a coating method commonly used in the art. For example, the coating method may be a spin method, a dipping method, a spray method, a roll coating method, a gravure printing method, a bar coating method, a die coating method, a comma coating method, or a mixed method thereof. The coating layer including the solid electrolyte may be in the form of a solid electrolyte film.

[0066] Further, a positive electrode current collector may be further formed on the other surface of the positive electrode active material layer. At this time, the positive electrode current collector and the positive electrode active material are not particularly limited as long as they are those commonly used in all-solid-state batteries.

[0067] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0068] Further, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly occluding and releasing lithium ions. For example, lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), Li[Ni x Co y Mn z M v O 2 (in the above formula, M is any one selected from the group consisting of Al, Ga, and In or two or more elements thereof; 0.3 ≦ x < 1.0, 0 ≦ y, z ≦ 0.5, 0 ≦ v ≦ 0.1, and x + y + z + v = 1), Li(Li a M b-a-b' M' b' )O 2-c A c(In the above formula, 0 ≦ a ≦ 0.2, 0.6 ≦ b ≦ 1, 0 ≦ b' ≦ 0.2, 0 ≦ c ≦ 0.2; M contains Mn and one or more selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more selected from the group consisting of Al, Mg, and B, and A is one or more selected from the group consisting of P, F, S, and N), such as layered compounds, and compounds substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y O 4 (where y is from 0 to 0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2 , etc., lithium manganese oxides; lithium copper oxide (Li 2 CuO 2 ); LiV 3 O 8 , LiFe 3 O 4 , V 2 O 5 , Cu 2 V 2 O 7 , etc., vanadium oxides; chemical formula LiNi 1-y MyO 2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is from 0.01 to 0.3), Ni-site type lithium nickel oxides represented by; chemical formula LiMn 2-y M y O 2 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is from 0.01 to 0.1) or Li 2 Mn 3 MO 8 (where M is Fe, Co, Ni, Cu, or Zn), lithium manganese composite oxides represented by; a part of Li in the chemical formula is replaced with alkaline earth metal ions, LiMn 2 O 4 ; disulfide compounds; Fe 2 (MoO 4 ) 3 , etc. can be mentioned, but it is not limited to only these.

[0069] Further, the positive electrode active material can be contained in an amount of 40 to 80% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40% by weight or more, or 50% by weight or more, and may be 70% by weight or less, or 80% by weight or less. If the content of the positive electrode active material is less than 40% by weight, the connectivity between the wet positive electrode active material layer and the dry positive electrode active material layer may be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0070] Further, as a component that assists in binding the positive electrode active material, the conductive material, etc. and binding to the current collector, the binder can include one or more selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphagen, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder can include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0071] Also, the binder can be contained in an amount of 1% by weight to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the binder may be 1% by weight or more, or 3% by weight or more, and may be 15% by weight or less, or 30% by weight or less. If the content of the binder is less than 1% by weight, the adhesion between the positive electrode active material and the positive electrode current collector may decrease. If it exceeds 30% by weight, the adhesion is improved, but the content of the positive electrode active material decreases accordingly, which may result in a lower battery capacity.

[0072] Also, the conductive material is not particularly limited as long as it can prevent side reactions in the internal environment of the all-solid-state battery and has excellent electrical conductivity without causing chemical changes to the battery. Typically, graphite or conductive carbon can be used. For example, graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, lamp black, thermal black; carbon-based substances with a crystal structure of graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives can be used alone or in combination of two or more, but it is not necessarily limited to this.

[0073] The conductive material can usually be contained in an amount of 0.5% by weight to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.5% by weight or more, or 1% by weight or more, and may also be 20% by weight or less, or 30% by weight or less. If the content of the conductive material is less than 0.5% by weight, it is difficult to expect an effect of improving electrical conductivity, or the electrochemical properties of the battery may deteriorate. If it exceeds 30% by weight, the amount of the positive electrode active material relatively decreases, and the capacity and energy density may decrease. The method of incorporating the conductive material into the positive electrode is not particularly limited, and ordinary methods known in the art, such as coating the positive electrode active material, can be used.

[0074] Further, the positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between the external lead wire and the positive electrode active material layer.

[0075] The positive electrode current collector is not particularly limited as long as it has high electron conductivity without causing a chemical change in the all-solid-state battery. For example, as the positive electrode current collector, copper, stainless steel, aluminum, nickel, titanium, palladium, fired carbon, those with a surface treatment of carbon, nickel, silver, etc. on the surface of copper or stainless steel, an aluminum-cadmium alloy, etc. can be used.

[0076] In order to strengthen the bonding force with the positive electrode active material layer, the positive electrode current collector can have a fine concavo-convex structure on its surface or adopt a three-dimensional porous structure. As a result, the positive electrode current collector can include various forms such as a film, a sheet, a foil, a mesh, a net, a porous body, a foam, a non-woven fabric body, etc.

[0077] The positive electrode as described above can be manufactured by a conventional method. Specifically, a composition for forming a positive electrode active material layer, which is manufactured by mixing a positive electrode active material, a conductive material, and a binder on an organic solvent, is applied and dried on a positive electrode current collector, and can be manufactured by selectively compression molding the current collector to improve the electrode density. At this time, as the organic solvent, it is preferable to use one that can uniformly disperse the positive electrode active material, the binder, and the conductive material and can be easily evaporated. Specifically, acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, etc. can be mentioned.

[0078] In the present invention, the negative electrode can be formed with a coating layer including a negative electrode active material layer and the solid electrolyte formed on one surface of the negative electrode active material layer. The method of forming the coating layer is the same as the method of forming the coating layer on the positive electrode.

[0079] Also, a negative electrode current collector may be further formed on the other surface of the negative electrode active material layer. At this time, the negative electrode current collector and the negative electrode active material are not particularly limited as long as they are those commonly used in all-solid-state batteries.

[0080] The negative electrode active material layer includes a negative electrode active material, a binder, and a conductive material.

[0081] The negative electrode active material can include a substance that can reversibly insert (intercalation) or deintercalate lithium (Li + ), a substance that can react with lithium ions to reversibly form a lithium-containing compound, lithium metal, or a lithium alloy.

[0082] The substance that can reversibly insert or deintercalate the lithium ions (Li + ) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The lithium ions (Li +Substances that can react with [[ID=]] to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitride, or silicone. The lithium alloy may be, for example, an alloy of a metal selected from the group consisting of lithium (Li) and sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0083] Preferably, the negative electrode active material may be lithium metal, specifically, in the form of a lithium metal thin film or lithium metal powder.

[0084] The negative electrode active material can be contained in an amount of 40 to 80% by weight based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% by weight or more, or 50% by weight or more, and may be 70% by weight or less, or 80% by weight or less. If the content of the negative electrode active material is less than 40% by weight, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0085] Also, the binder is as described above in the positive electrode active material layer.

[0086] Also, the conductive material is as described above in the positive electrode active material layer.

[0087] Further, the negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, the negative electrode current collector can be copper, stainless steel, aluminum, nickel, titanium, fired carbon, or a surface-treated material of copper or stainless steel with carbon, nickel, titanium, silver, etc. on its surface, or an aluminum-cadmium alloy, etc. Also, similar to the positive electrode current collector, the negative electrode current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc. with fine irregularities formed on its surface.

[0088] The method for manufacturing the negative electrode is not particularly limited, and the negative electrode active material layer can be formed and manufactured by using a method for forming a layer or film commonly used in the art on the negative electrode current collector. For example, methods such as pressing, coating, and vapor deposition can be used. Also, when the battery is assembled with no lithium thin film on the negative electrode current collector and a metallic lithium thin film is formed on the sheet metal by initial charging, it is also included in the negative electrode of the present invention.

[0089] The present invention also relates to an all-solid-state battery including the all-solid-state battery electrode.

[0090] Among the positive electrode and the negative electrode included in the all-solid-state battery, one or more may have a coating layer containing a solid electrolyte as described above.

[0091] Since the solid electrolyte exhibits excellent characteristics in both ion conductivity and electrical conductivity, when applied to an all-solid-state battery in the form of a coating layer formed on the positive electrode and / or the negative electrode, the performance and life characteristics of the all-solid-state battery can be improved.

[0092] Hereinafter, preferred embodiments are presented to assist in understanding the present invention. However, the following embodiments are merely illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the scope of the technical idea, and such changes and modifications naturally belong to the scope of the appended claims.

[0093] In the following Examples and Comparative Examples, solid electrolytes were produced according to the weight ratios of a mixed conductive polymer, a binder, and a lithium salt as described in Table 1 below.

[0094]

Table 1

[0095] Example 1 5 g of a solution of PEDOT:PSS (Sigma-Aldrich, 1.1 wt%), which is a mixed conductive polymer, and 0.11 g of LiTFSI, which is a lithium salt, were sufficiently stirred for 12 hours to obtain a first mixed solution. Then, 2 mg of SBR, which is a binder, was added to obtain a second mixed solution. The second mixed solution was coated on a stainless-steel foil with a doctor blade to form a coating layer. The weight ratio of the mixed conductive polymer, lithium salt, and binder ((PEDOT:PSS):LiTFSI:SBR) was 27.5:55:1. The weight ratio of PEDOT to PSS was 1:2.5.

[0096] Thereafter, it was vacuum-dried at 100 °C for one day to remove the solvent in the second mixed solution, and a solid electrolyte membrane was produced.

[0097] Example 2 A solid electrolyte membrane was produced in the same manner as in Example 1, except that the weight ratio of the mixed conductive polymer, lithium salt, and binder was 11:22:1.

[0098] Example 3 A solid electrolyte membrane was produced in the same manner as in Example 2, except that CMC was used instead of SBR as the binder.

[0099] Comparative Example 1 A solid electrolyte membrane was produced in the same manner as in Example 1, except that PEO was used instead of the mixed conductive polymer, no binder was used, and the weight ratio of PEO and LiTFSI, which is a lithium salt, was 10:1.

[0100] Comparative Example 2 A solid electrolyte membrane was produced in the same manner as in Example 1, except that only PEDOT:PSS, a mixed conductive polymer, was used.

[0101] Comparative Example 3 A membrane was produced in the same manner as in Example 1, using only SBR as a binder.

[0102] Comparative Example 4 A solid electrolyte membrane was produced in the same manner as in Example 1, except that the weight ratio of the mixed conductive polymer to the binder was 11:1 without using a lithium salt.

[0103] Comparative Example 5 An electrolyte membrane was produced in the same manner as in Example 1, except that no mixed conductive polymer was used and the weight ratio of the lithium salt to the binder was 22:1.

[0104] Experimental Example 1: Evaluation of Solid Electrolyte For the solid electrolyte membranes produced in the examples and comparative examples, tests on ionic conductivity and electrical conductivity were carried out as follows, and the results are shown in Table 2 below.

[0105] (1) Ionic Conductivity After the solid electrolyte membrane was brought into contact with a stainless steel plate to form a coin cell, an alternating voltage was applied at room temperature. At this time, the measurement frequency was set in the amplitude range of 500 kHz to 20 MHz under the applied conditions, and the impedance was measured using VMP3 of BioLogic. Using the following formula 1, the resistance of the solid electrolyte membrane was obtained from the intersection point (Rb) where the semicircle or straight line of the measured impedance locus meets the real axis, and the ionic conductivity (σ) of the solid electrolyte membrane was calculated from the area and thickness of the sample.

[0106] [Formula 1] [Number] σ: Ionic Conductivity Rb: Intersection point of the impedance locus and the real axis A: Area of the sample t: Thickness of the sample

[0107] (2) Electrical conductivity (S) Cyclic voltammetry measurement (-0.1 V to 0.1 V) was performed on a coin cell fabricated with the same structure as the coin cell fabricated during the ion conductivity measurement, and the electrical conductivity was calculated using the following formula 2.

[0108] [Formula 2] S = A / V × Film thickness / film dimension A: Current V: Voltage Film thickness: Thickness of the sample Film dimension: Width of the sample

[0109]

Table 2

[0110] As shown in Table 2 above, it was found that the ion conductivities of the mixed conductive polymers of Examples 1 to 3 are superior to those of the PEO solid electrolyte membrane of Comparative Example 1, which is a general solid electrolyte membrane.

[0111] As described above, although the present invention has been described with reference to the limited examples and drawings, the present invention is not limited thereby, and it goes without saying that various modifications and variations can be made by those having ordinary knowledge in the technical field to which the present invention pertains within the equivalent scope of the technical idea of the present invention and the following claims.

Claims

1. A solid electrolyte comprising a mixed conductive polymer having ionic conductivity and electrical conductivity characteristics, a binder, and a lithium salt, wherein it contains 100 parts by weight of the mixed conductive polymer, 2 to 30 parts by weight of the binder, and 100 to 300 parts by weight of the lithium salt with respect to 100 parts by weight of the mixed conductive polymer.

2. The solid electrolyte according to Claim 1, wherein the mixed conductive polymer contains one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)), polyacetylene, poly(paraphenylene), poly(paraphenylene)sulfide, polythiophene, polypyrrole, polyisothianaphthalene, poly(paraphenylene vinylene), polyaniline, and poly(3,4-ethylenedioxythiophene).

3. The binder includes one or more selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphagen, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride and poly(vinylidene fluoride)-hexafluoropropene. The solid electrolyte according to claim 1.

4. The lithium salt is one or more selected from the group consisting of LiTFSI (Lithium bis(trifluoromethanesulphonyl)imide), LiFSI (Lithium bis(fluorosulphonyl)imide), LiNO ３ , LiOH, LiCl, LiBr, LiI, LiClO ４ , LiBF ４ , LiB １０ Cl １０ , LiPF ６ , LiCF ３ SO ３ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiAlCl ４ , CH ３ SO ３ Li, CF ３ SO ３ Li, LiSCN, LiC(CF ３ SO ２ ), ３ , (CF ３ SO ２ ), ２ NLi and (FSO ２ ), ２ The solid electrolyte according to claim 1, which contains one or more selected from the group consisting of NLi.

5. The solid electrolyte according to claim 1, wherein the lithium salt is dissociated and contained inside a mixed-conductive polymer matrix containing a mixed-conductive polymer and a binder.

6. The solid electrolyte according to claim 1, wherein the solid electrolyte is in the form of a solid electrolyte membrane.

7. The solid electrolyte according to claim 1, wherein the thickness of the solid electrolyte is 10 to 60 μm.

8. (S1) Coating a mixed solution obtained by adding a mixed-conductive polymer, a binder and a lithium salt to a solvent onto a substrate; and (S2) Drying the coating layer obtained in step (S1); A method for producing a solid electrolyte according to any one of claims 1 to 7.

9. The manufacturing method of the solid electrolyte according to claim 8, wherein the coating method is bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating or solution casting.

10. The manufacturing method of the solid electrolyte according to claim 8, wherein the drying is performed at 300 °C or lower.

11. The manufacturing method of the solid electrolyte according to claim 8, wherein the substrate is stainless steel, polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film or polyimide film.

12. The manufacturing method of the solid electrolyte according to claim 8, wherein the solvent is at least one selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, N,N-dimethylformamide (DMF), benzene, tetrahydrofuran (THF) and water.

13. An electrode for all-solid-state battery having a coating layer containing the solid electrolyte according to claim 1.

14. The electrode according to claim 13, wherein the electrode for all-solid-state battery is a positive electrode or a negative electrode.

15. An all-solid-state battery including the electrode according to claim 13.

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